Model equilibrium splits using K-values or Raoult options. Get phase compositions, flowrates, and checks instant. Designed for engineers who need fast, clear outputs always.
| Component | z | K |
|---|---|---|
| Methane | 0.50 | 6.80 |
| Ethane | 0.30 | 2.20 |
| Propane | 0.20 | 0.90 |
The flash calculation assumes equilibrium with yᵢ = Kᵢ xᵢ and an overall feed composition zᵢ. The unknown vapor fraction V satisfies the Rachford–Rice equation:
Once V is found, phase compositions are computed as:
For the ideal method, Kᵢ is calculated using Raoult’s law: Kᵢ = Pᵢˢᵃᵗ / P, where Pᵢˢᵃᵗ comes from the Antoine correlation.
A flash model starts with feed flow F and composition zi. This calculator accepts any F unit label, then uses zi to compute component feed rates F·zi for traceability. If zi do not sum to 1.0, they are normalized and the original sum is flagged. For preliminary work, 3–10 components are typical, and you can add rows for larger mixtures. Use a consistent basis when comparing scenarios across cases.
The key outputs are vapor fraction V, vapor flow V·F, and liquid flow (1−V)·F. Phase compositions are computed as xi = zi/(1+V(Ki−1)) and yi = Ki·xi, then renormalized so Σxi and Σyi equal 1.0 within rounding. The table also reports L·xi and V·yi, so you can check F·zi ≈ L·xi + V·yi. Iterations are displayed; 10–60 steps are common for tight tolerances.
Supply Ki directly when you already have equilibrium ratios from simulation, correlations, or lab data. For ideal screening, the Raoult option estimates Ki = Psat/P using Antoine constants at the selected temperature. Pressure is converted to bar and temperature to °C before evaluating Psat. Because Antoine sets vary by source and validity range, keep constants consistent and avoid large extrapolation. With custom K, refresh values for each pressure–temperature case.
Flash behavior shifts with operating conditions. At higher pressure, Ki often decreases and V tends to drop, increasing liquid yield; at higher temperature, Psat rises and V often increases. Use quick cases, for example 8–20 bar and 20–80 °C, while holding feed constant. When V approaches 0 or 1, the solver reports a single-phase outcome, helping you spot dew or bubble proximity.
Export results as CSV for spreadsheets or as PDF for design notes and approvals. The CSV preserves zi, Ki, xi, yi, and split flowrates for downstream sizing checks. The PDF uses a landscape table layout for readability in formal reviews. Include your assumptions alongside exports: equilibrium method, property source, and operating conditions.
V is the fraction of the total feed that leaves as vapor on a molar basis. Multiply V by F for vapor flow, and (1−V) by F for liquid flow. It summarizes the split at the selected conditions.
If the entered zi values do not sum to 1.0, the tool scales them so Σzi equals 1.0. This preserves relative proportions while ensuring the flash equations are well-posed. The original sum is shown as a warning.
Use custom K-values when you have reliable equilibrium ratios from a property package, EOS work, or experimental data. They are often more accurate for hydrocarbons at high pressure or for non-ideal mixtures than ideal screening.
Yes. If the Rachford–Rice function does not change sign between V=0 and V=1, the tool reports a single-phase result. This helps identify cases near bubble or dew limits during sensitivity studies.
Select a consistent Antoine constant set for each component and keep within its published temperature range. Different databases may use different units or forms, so verify the correlation format matches the inputs before trusting Psat and K values.
Exports include operating conditions and the component table with zi, Ki, xi, yi, and component split flowrates. CSV is suited for further calculations, while PDF is formatted for sharing in design notes and review packages.
Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.